Reconditioning oils



Patented Aug. 11, 1931 UNITE STAT PATEN FFEE JAMES G. FORD, OF 'WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO VIESTINGI'IOUSE" ELECTRIG & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA RECONDI TIONING OILS No Drawing.

1 carbon oils the alcohols, aldehydes, ketones,

esters, acids and other organic bodies derived from the oxidation of the oils.

Another object of my invention is to provide a process for reconditioning oxidized oils that contain asphaltic sludge and other products of oxidation without changing the character of the oil with respect to its contents of saturated and unsaturated hydrocarbons.

WVhen mineral oils are subjected to heat in the presence of oxidizing gases or to electrical discharge in the presence of such gases, the oil becomes charged with oxidized hydrocarbons which are manifested mainly as 5 carbonaceous sludge and as liquids that are acidic in character. The oil becomes sluggish and reactive towards materials such as metal and organic insulating materials and, as a result of the oxidization of the oil, the

dissipation of heat through the oil and the insulation of conductors immersed therein becomes diminished.

It is the practice in refining lubricating and insulating oil, to treat it for a short time with an excess of sulphuric acid, to remove the acid by decantation, neutralization and washing, and then to dry the oil with calcium chloride or anhydrous sodium caibonate. The dried oil is sometimes treated with fullers earth and filtered in order to remove coloring matter. As a rule, this process partially removes the acids and other oxidized hydrocarbon products and unsaturates, but it does not completely remove all of them. Furthermore, in this process, it is difficult to remove all the water that is used to wash out the sulphuric acid.

If sulphuric acid, an oxidized product or water is present, the oil is unsuitable or inferior for lubricating and insulating pur- Application filed August 6, 1927. Serial No. 211,266.

poses, and if the mineral oil is deficient in unsaturates, it will oxidize easily and a large amount of acidity will develop in service in a short time.

'My invention provides a method for treating mineral hydrocarbon oils and removing the oxidized products without materially effectin the relative amount of unsaturates in the oil, and is particularly useful for reconditioning or refining mineral oils that have been oxidized in transformersor other oilfilled electrical apparatus. In reconditioning mineral oils, 1 may add concentrated sulphuric acid having a specific gravity of 1.84:

but I prefer to use for this purpose a commercial 15% fuming sulphuric acid which is known as oleimi, as I find that the action of an acid having this concentration is more rapid and complete. The amount of oleum added is sufficient to react with all the oxid- 7 ized products present, but insufficient to react with the unsaturated hydrocarbons. The acids, esters and sludge react with the oleum, but the unsaturates are practically unchanged when the oil is treated with the proper amount of acid for the correct period of time.

lVhen the oil is thus treated, the oxidized products are precipitated or dissolved in the acid as sulphonated compounds, although a small amount of the acid and sulphonated compounds remain in the oil. I prefer to use only a slight excess of the fuming sulphuric acid, thus ensuring the removal of all of the oxidation products without substantially affecting the amount of unsaturated hydrocarbons that is present. The amount of oleum to be used with oils of various contents of oxidized products may be determined by well: known quantitative methods of analysis or by trial. I have found that oleum in amounts ranging from 2 to 4 per cent of the weight of the oil is sufiicient for most oils, the quantity ofacid used varying with the quality of the oil.

If the oil is treated with the proper amount of oleum to react with the organic oxidation products, the relative amount of unsaturated hydrocarbons remains substantially unaltered in the oil. There might be a slight diminu thoroughly mixed? process, by

tion of the unsaturated hydrocarbons, particularly when too large an excess of acid is used, or when the treatment has been carried on for an excessive period of time, but the di -minutioi1 in one cycle consisting of an'oxida-,

tion and a reconditioning is practically insignificant, if the process is properly conducted with respect to the amount of acid and the time of treatment. 7

In practicing my invention,'the fuming sulphuricacid, together with fullers earth, is added to'the oil and the mixture is agitated for a sufficient length of time in' a suitable container t9 enable the ingredients to be The time of agitation will depend somewhat on the condition of the oil but ordinarily will net exceed fifteen minutes. I have found that the addition ef fullers earth to the acid and oil, followed by a thorough agitation, causes the acid sludge to be removed almost immediately. The sulphuric acid, the acid sludge, fullers earth and other impurities settle to thebottoni of the container and may be drained off or, if preferred, the purified oil may be decanted. An oil purified in this manner is much clearer and lighter in color than that obtained by the usual method, but contains sulphur dioxide in solution.

Silica gel is now added to the oil to remove any residual sulphonated products or sulphuric acid that may remain in the oil. The mixture of silica gel and oil is heated to a temperature of about 120 C. and maintained at this temperature for about an hour. The mixture is thoroughly agitated, during this means of stream of gas, such as nitrogen or carbon dioxide, or even air ma be used, although I prefer to use an inert gas. The gas not only agitates the mixture, but assists in the removal of the sulphur dioxide, and should be passed through the mixture until the odor of thatgas is no longer apto be limited only by the prior art and by the appended claim. 7 1

I claim as my invention: 3 In the process of refining mineral oils that have been used in transformers or other oilfilled apparatus, the step which comprises treating the oil with from two to four percent of fuming sulphuric acid mixed with fullers earth, agitating the mixture :and removing the water, oxidized hydrocarbon products rmd residual sulphuric acid after they have separated from the oil. I

In testimony whereof, I have hereunto subscribed my name this 3rd day of August, 1927.

7 JAMES G. FORD.

parent. The oil may be decanted, filtered or centrifuged to remove the residual fullers earth, thesilica gel and the adherent residue of oxidized products and acid. The amount of silica gel added is that whichis suflicient to absorbthe objectionable residue in the, oil, about 5 per cent of the weight of oil being usually sufficient. 1 f

The resultant product is 'an oil containing substantially the same amount of unsaturates as the original oil with the exception of the unsaturated con'upounds that were'oxidiZe-d in service, and it is dry and free from oxidation products and acid. If desired, the *amount of unsaturates in the oil may be in creased or decreased by mixing the oil with another oil containing a higher or lower content of unsaturates, as the case may be.

lVhile T have described a specific embodiment of my invention, various modifications may be made without departing from the spirit and scope thereof. I desire, therefore, 

